The present invention relates generally to the tempering of glass sheets and, more particularly, to an improved apparatus for supporting and conveying thin glass sheets through a horizontal tempering station.
In a horizontal flat glass tempering operation, heated flat sheets of glass are successively advanced in a generally horizontal plane along a substantially horizontal path on a series of driven conveyor rolls through opposed blastheads of a chilling or tempering station whereby the opposite surfaces of the heated sheets are flushed with a suitable cooling medium, such as air for example, to rapidly chill the glass sheets and impart the desired temper thereto. The air under pressure is directed in streams by a plurality of opposed nozzles against the opposite glass surfaces. The pressures directed against such opposite surfaces may vary, sometimes being greater against the bottom surface than the top surface and vice versa. The weight and mass of glass sheets of conventional thicknesses are sufficient to maintain the same in engagement with the conveyor rolls so as to be advanced thereby. However, when processing thin glass sheets, i.e. sheets having thicknesses of 1/8 inch and less, there is a tendency for the sheets to float off the rolls with consequent interruption in their advancement and the possibility of damage thereto due to their engagement either with succeeding sheets or with the nozzles of the upper blasthead.
Accordingly, it is desirable to provide a series of upper conveyor rolls in closely spaced vertical relation to the usual lower conveyor rolls within the tempering section to restrain upward movement of the sheets and to assist in their advancement through the tempering section. However, employing a second series of conveyor rolls requires additional drive train components and materially encumbers the drive end area of the rolls, seriously impeding access into the tempering area between the blastheads for maintenance and cullet removal. Also, because of the close vertical spacing between the upper and lower rolls, there is a definite possibility of glass jamming within the tempering section in the event of glass breakage. Any such breakage also tends to back-up and create jamming within the furnace due to the close proximity of the furnace exit end to the tempering section in conventional tempering operations.